Oil jet for internal combustion engine and piston cooling device for internal combustion engine

ABSTRACT

An oil jet (23) has an injection nozzle (32) that injects engine oil supplied from an oil supply passage of the internal combustion engine toward a piston. The injection nozzle (32) has a first pipe (36) having a supply port (35) communicating with an oil supply passage side and a second pipe (38) having an injection orifice (37) that injects the engine oil. The first pipe (36) and second pipe (38) are joined together with their axes forming a predetermined angle. The injection orifice (37) is formed such that a cross section of the injection orifice (37) is greater than a minimum radial direction cross section of the first pipe (36).

TECHNICAL FIELD

The present invention relates to an improvement in an oil jet for an internal combustion engine and a piston cooling device for the internal combustion engine.

BACKGROUND ART

As is known, an oil jet of an internal combustion engine is an oil jet that reduces a temperature of a piston by jetting or spraying engine oil to a back surface side of the piston, increases strength of the piston, ensures reliability of the piston and reduces an engine knocking.

In order to contribute to recent improvement in fuel efficiency of the internal combustion engine, reduction in size and increase in energy efficiency of an oil pump that produces pressure of the engine oil and reduction in supply amount of the engine oil to the oil jet are desired, and there is a need to perform efficient heat exchange with a small amount of oil. Here, a general conventional oil jet is configured to linearly inject or spray the oil with an oil flow velocity increased by a structure in which a tip end of an injection orifice side is narrowed or squeezed. Because of this, jet (injection flow) of the oil has a high linearity, and a jet diameter (an injection flow diameter) of the oil is about a diameter of a nozzle tip end, then cooling is locally performed. It is therefore impossible to efficiently cool the entire piston.

Thus, Patent Document 1 has disclosed various shapes of a tip end portion of the oil jet and a technique of controlling a shape of the jetted oil (the injected oil). Further, Patent Document 2 has proposed a structure in which a spiral groove is formed on a pipe inner surface of the oil jet.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Unexamined Utility Model Application     Publication No. JIKKAIHEI 4-105935 (JPH04-105935U) -   Patent Document 2: Japanese Unexamined Utility Model Application     Publication No. JIKKAISHO 50-52341 (JPU11975-052341)

SUMMARY OF THE INVENTION Technical Problem

In Patent Document 1, however, forming the various shapes of a nozzle tip end of the oil jet causes increase in manufacturing man-hours and manufacturing cost. In Patent Document 2, it is extremely technically difficult to form the spiral groove on a curved pipe inner surface of the oil jet, and this also increases manufacturing man-hours and manufacturing cost.

An object of the present invention is therefore to provide a new oil jet for an internal combustion engine and a new piston cooling device for the internal combustion engine, which can be formed by easy manufacturing and process and is capable of widely injecting or spraying the engine oil with a high cooling effect.

Solution to Problem

The present invention relates to an oil jet for an internal combustion engine as a cooling device that is provided inside the internal combustion engine and injects or sprays the oil toward a back surface side of a piston. The oil jet comprises an injection nozzle that injects the oil supplied from an oil supply passage of the internal combustion engine toward the piston. The injection nozzle has a first pipe communicating with the oil supply passage and a second pipe having an injection orifice that injects the oil. The first and second pipes being joined together with axes of the first and second pipes forming a predetermined angle. The injection orifice is formed such that a cross section of the injection orifice is greater than a minimum radial direction cross section of the first pipe.

Effects of Invention

According to the present invention, it is possible to widely inject or spray the engine oil and greatly increase cooling efficiency although the manufacturing and process are easy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an example of an internal combustion engine to which an oil jet for an internal combustion engine of the present invention is applied.

FIG. 2 is a bottom view of a piston, viewed from a back surface side of the piston.

FIG. 3 is a perspective view showing an oil jet for the internal combustion engine according to a first embodiment of the present invention.

FIG. 4 is a sectional view showing the oil jet for the internal combustion engine according to the first embodiment.

FIGS. 5A to 5D are explanatory drawings schematically showing a flow of engine oil in an injection nozzle in time sequence, according to the first embodiment.

FIGS. 6A and 6B are explanatory drawings schematically showing an injection pattern or an injection form of the engine oil of a reference example (6A) and the first embodiment (6B).

FIG. 7 is a characteristic showing an experimental result of the presence or absence of occurrence of a cavity with respect to a diameter of a second pipe, a ratio of the diameter of the second pipe and a ratio of a cross section of the second pipe.

FIG. 8 is a perspective view showing a principal part of the oil jet for the internal combustion engine according to a second embodiment of the present invention.

FIGS. 9A to 9E are explanatory drawings schematically showing a flow of the engine oil in the injection nozzle in time sequence, according to the second embodiment.

FIG. 10 is an explanatory drawing schematically showing an injection pattern or an injection form of the engine oil according to the second embodiment.

FIGS. 11A and 11B are explanatory drawings for explaining test details of the oil jet according to the second embodiment.

FIG. 12 is an explanatory drawing showing a test result of the oil jet according to the second embodiment.

FIG. 13 is a perspective view showing a principal part of the oil jet for the internal combustion engine according to a third embodiment of the present invention.

FIG. 14 is a sectional view showing the principal part of the oil jet for the internal combustion engine according to the third embodiment.

FIG. 15 is a sectional view showing a principal part of the oil jet for the internal combustion engine according to a fourth embodiment of the present invention.

FIG. 16 is a perspective view showing an oil jet for the internal combustion engine according to a fifth embodiment of the present invention.

FIG. 17 is a sectional view showing the oil jet for the internal combustion engine according to the fifth embodiment.

FIG. 18 is a sectional view showing a modified example of a supply pipe of the fifth embodiment.

FIG. 19 is a perspective view showing an oil jet for the internal combustion engine according to a six embodiment of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the following description, an oil jet for an internal combustion engine and a piston cooling device for the internal combustion engine according to the present invention will be explained with reference to drawings.

As shown in FIG. 1, in a cylinder block 10, a cylindrical cylinder liner 11 is provided. A piston 12 is provided so as to be able to reciprocate in the cylinder liner 11. The cylinder liner 11 is provided with a water jacket 13 where cooling water flows. The piston 12 is a bottomed-cylindrical-shaped piston that is cast in aluminum alloy or metal material such as cast iron. A piston upper portion 16, which has a piston crown surface 15 facing a combustion chamber 14 that is formed at an upper side of the piston 12, of the piston 12 is provided with a plurality of ring grooves 17 on an entire circumference of the piston 12 in a circumferential direction. A piston ring (not shown) is fitted on each ring groove 17. By this piston ring, a gap between the piston 12 and an inner surface of the cylinder liner 11 is sealed, and engine oil adhering to the inner surface of the cylinder liner 11 is scraped off. The piston 12 is provided at a lower portion thereof with a cylindrical skirt portion 18 that extends downward in a thrust-counter thrust direction orthogonal to a piston pin 21. The piston 12 is configured such that inclination or leaning of the piston 12 is suppressed by this skirt portion 18.

As shown in FIGS. 1 and 2, pin boss portions 19 of the piston 12 and an upper end of a connecting rod 20 are connected together so as to relatively rotate with the piston pin 21 that is inserted into the both of the pin boss portions 19 and the connecting rod 20. A lower end of the connecting rod 20 is rotatably connected to a crank pin 22 of a crankshaft. Therefore, pressure (load) of combustion gas that ignites in the combustion chamber 14 which the piston crown surface 15 faces is transmitted to the crank pin 22 of the crankshaft through the piston pin 21 and the connecting rod 20.

The cylinder block 10 is provided with an oil jet 23 as a cooling device of the internal combustion engine. This oil jet 23 has the function of cooling the piston 12 by injecting or spraying and supplying the engine oil toward a back surface side of the piston 12. The oil jet 23 is connected and secured to a mounting surface 24 at a lower end of the cylinder liner 11 with a fixing bolt 25 so as not to interfere with the connecting rod 20 and the crankshaft.

The cylinder block 10 is further provided with an oil supply passage 26 to supply the engine oil to an oil supply portion including the oil jet 23. The engine oil stored in an oil pan disposed at a lower side of the internal combustion engine is pressurized by an oil pump, and supplied to the oil jet 23, lubrication parts and hydraulic devices and so on through the oil supply passage 26, although these are not illustrated in the drawings.

As a representative structure of the oil jet 23, a die-cast type as shown in FIG. 18, a brazing two-piece type as shown in FIGS. 16 and 17 and a brazing integral type as shown in FIGS. 3 and 4 are raised. In a case of the die-cast type and the brazing two-piece type, typically, the oil jet is connected and secured to the cylinder block 10 with a fixing bolt having therein a check ball. In a case of the brazing integral type having therein a valve structure, the oil jet could be secured to the cylinder block side with a normal fixing bolt having no check ball.

As is known, the check ball is forced in a direction that closes the oil supply passage 26 by a spring, which is not illustrated in the drawings, and by the fact that pressure of the engine oil in the oil supply passage 26 (in a main gallery) exceeds a set load of the spring, the engine oil is supplied to the oil jet 23. That is, when the pressure of the engine oil supplied to the oil supply passage 26 of the internal combustion engine is equal to or greater than a predetermined value, the engine oil spontaneously jets. As described later, the engine oil flowing into the oil jet 23 is injected or sprayed and supplied to the back surface side of the piston crown surface 15 through an inner pipe of the oil jet 23.

FIGS. 3 and 4 show a first embodiment in which the present invention is applied to a brazing integral type oil jet 23A. An oil jet body 30 of the oil jet 23A is provided with a cylindrical bolt insertion hole 31 into which the fixing bolt 25 having therein the check ball is loosely inserted. Further, a tubular injection nozzle 32 is formed integrally with the oil jet body 30. The engine oil flows into a bolt internal passage 33 that is formed along an axis of the fixing bolt 25 from the oil supply passage 26 in the cylinder block 10, and is injected or sprayed and supplied to the piston 12 through a cylindrical passage 34 that is a space formed between an outer circumference of the fixing bolt 25 and an inner circumference of the bolt insertion hole 31 and a pipe of the injection nozzle 32.

The injection nozzle 32 has a first pipe 36 having a supply port 35 communicating with the cylindrical passage 34 side (the oil supply passage 26 side) and a second pipe 38 having an injection orifice 37 located at an outlet side and injecting or spraying the engine oil. These first pipe 36 and second pipe 38 are connected or joined together with their axes forming a predetermined angle (in this embodiment, a substantially 90 degrees).

The first pipe 36 is shaped into a linear shape having the same radial direction cross section (a passage cross section) including the supply port 35. The second pipe 38 is shaped into a linear shape having the same radial direction cross section including the injection orifice 37, and is formed so as to be sufficiently greater than the supply port 35 and a minimum radial direction cross section of the first pipe 36. More specifically, the second pipe 38 is formed such that a minimum radial direction cross section of the second pipe 38 is four times the minimum radial direction cross section of the first pipe 36 or more.

FIGS. 5A to 5D are explanatory drawings schematically showing a flow of the engine oil in the injection nozzle 32 in time sequence. As shown in FIG. 5A, first, the engine oil flows from the narrow first pipe 36 whose passage cross section is small into the second pipe 38 whose passage cross section is large. Subsequently, as shown in FIG. 5B, the engine oil collides with or strikes an inner circumferential surface of the second pipe 38 which is located at an opposite side to the first pipe 36 (at a left side in FIG. 5B) by inertia of the flowing engine oil.

Further, as shown in FIG. 5C, the engine oil having struck the inner circumferential surface of the second pipe 38 flows while returning to both sides from a collision point so as to fold or round along the inner circumferential surface of the second pipe 38. Therefore, finally, as shown in FIG. 5D, bipolar vortexes arise in the second pipe 38, and two cavities 40 are formed at both sides of an axis of the first pipe 36. By the fact that the cavities 40 are generated in this way, the flow of the engine oil injected or sprayed from the injection orifice 37 becomes unstable, and the engine oil jets (is injected or sprayed) while being mixed with air.

FIG. 6A shows a reference example in which the minimum cross section of the second pipe 38 is smaller than the minimum cross section of the first pipe 36. In this reference example, since an oil flow velocity is high and the engine oil jets almost linearly, jet (injection flow) of the engine oil has a high linearity, and a jet diameter (an injection flow diameter) of the engine oil is about a bore (a diameter) of the injection orifice. Because of this, cooling is locally performed, and it is impossible to efficiently cool the entire piston.

In contrast to this, as shown in FIG. 6B, in the present embodiment in which the minimum radial direction cross section of the second pipe 38 is greater than the minimum radial direction cross section of the first pipe 36, as described above, since the engine oil is injected or sprayed while being mixed with air, the flow of the engine oil is not a continuous flow like the reference example, but a continual or intermittent flow of droplets. By such flow of the droplets being generated, an injection range (an injection area) of the engine oil is broadened, and droplets of the engine oil are easily scattered when contacting the back surface side of the piston crown surface 15. As a consequence, an effect of broadening a substantial injection range (area) can be obtained, and an amount of heat transfer is increased, then cooling efficiency can be greatly increased.

FIG. 7 shows an experimental result of the presence or absence of occurrence of the cavity 40 in the second pipe 38 with respect to a minimum diameter of the second pipe 38, a ratio of the minimum diameter of the second pipe 38 to a minimum diameter of the first pipe 36 and a ratio of the minimum radial direction cross section of the second pipe 38 to the minimum radial direction cross section of the first pipe 36. As shown in lower side two rows in FIG. 7, it was found and verified that the above mentioned cavities 40 occurred in the second pipe 38 when the diameter of the second pipe 38 is double the diameter of the first pipe 36 or more and the minimum radial direction cross section of the second pipe 38 is four times the minimum radial direction cross section of the first pipe 36 or more.

Next, an oil jet 23B of a second embodiment of the present invention will be explained with reference to FIGS. 8 to 10. In the following explanation, the same element or component as that of the above embodiment is denoted by the same reference sign, and its explanation is omitted. In this second embodiment, an axis 36A of the first pipe 36 is offset from an axis 38A of the second pipe 38 by a predetermined offset amount e (see FIGS. 9A to 9D).

FIGS. 9A to 9D are explanatory drawings, similar to FIGS. 5A to 5D, schematically showing a flow of the engine oil in the injection nozzle 32 in time sequence. As shown in FIG. 9A, first, the engine oil flows from the narrow first pipe 36 whose passage cross section is small into the second pipe 38 whose passage cross section is large. Subsequently, as shown in FIG. 9B, the engine oil collides with or strikes an inner circumferential surface of the second pipe 38 which is located at an opposite side to the first pipe 36 (at a left side in FIG. 9B) by inertia of the flowing engine oil.

At this time, in the second embodiment, since the axis 36A of the first pipe 36 is offset from the axis 38A of the second pipe 38 to a lower side in FIG. 9B, as shown in FIG. 9C, much of the engine oil having struck the inner circumferential surface of the second pipe 38 flow to an opposite side to an offset direction (i.e. an upper side in FIG. 9C), namely, that much of the engine oil flow in a clockwise direction, then one turning flow Y1 in the clockwise direction occurs. Here, as shown in FIG. 9E, even if the passage cross section of the second pipe 38 is not large, a turning flow Y2 occurs. Then, finally, one cavity 41 could be generated in the opposite side to the offset direction in the second pipe 38, as shown in FIG. 9D.

In this manner, in the second embodiment, since the injection of the engine oil is performed while maintaining the turning flow Y1 in the second pipe 38, as shown in FIG. 10, first, a liquid film expanding in a radial direction is formed immediately after the injection. Then, when this liquid film flows forward and dissipates or disappears, the flow of the engine oil is changed to the flow of the droplets. Accordingly, in addition to the same effect as the first embodiment, by the turning flow Y1 formed by the offset arrangement, the injection range (the injection area) of the engine oil is further broadened, then good cooling characteristic can be obtained.

If the offset amount e is too large, the turning flow Y1 is too strong, then linearity of spray is degraded. It is therefore preferable to set the offset amount e to within a certain limited range. To check the linearity with respect to the offset amount, as shown in FIGS. 11A and 11B, a change of flow of the liquid film was checked by a flow amount of the engine oil passing through a surface of a diameter of 8 mm which is located at 50 mm from the injection orifice 37. Its result is shown in FIG. 12. As shown in FIG. 12, it was verified that when the offset amount e with respect to an outlet diameter that is a diameter of the injection orifice 37 exceeds 15%, as shown in FIG. 11B, the linearity was lost and the liquid film was in an expanding direction, and the engine oil was diffused immediately after the injection, then the engine oil did not reach the back surface side of the piston crown surface 15. It is therefore desirable to set the offset amount e with respect to the diameter (the outlet diameter) of the injection orifice 37 to be equal to or less than 15%. Preferably, it is 10% or less.

FIGS. 13 and 14 show a third embodiment of the present invention. In this third embodiment, a second pipe 38C is molded into a long hole shape by a plurality of drilling processes. In a fourth embodiment of the present invention shown in FIG. 15, a second pipe 38D is formed into a cone or a frustum of a cone whose radial direction cross section is gradually increased toward the injection orifice 37. Shapes of the second pipes 38C and 38D of the third and fourth embodiments also bring about the same working and effect as those of the first and second embodiments.

FIGS. 16 and 17 show a fifth embodiment of the present invention in which the present invention is applied to the brazing two-piece type oil jet. Similar to the first embodiment, an oil jet body 30 of the oil jet is provided with a cylindrical bolt insertion hole 31 into which the fixing bolt 25 having therein the check ball is loosely inserted. In this fifth embodiment, an injection pipe 43, which is a separate element from the oil jet body 30, is secured to the oil jet body 30. This injection pipe 43 forms a part of the injection nozzle 32 having the injection orifice 37. The injection pipe 43 has a constant radial direction cross section, and a curved portion (or a bending portion) 44 is provided at some midpoint in the injection pipe 43 as appropriate.

Further, a supply pipe 45 to which the injection pipe 43 is connected is formed integrally with the oil jet body 30. This supply pipe 45 has a radial direction cross section that is set to be smaller than that of an inside of the injection pipe 43.

Therefore, in a case of a configuration of the fifth embodiment, a section of the injection pipe 43 at an injection orifice 37 side with respect to the curved portion 44 forms the second pipe 38. A section of the injection pipe 43 at a side opposite to the injection orifice 37 with respect to the curved portion 44 and the supply pipe 45 provided with the supply port 35 form the first pipe 36. Then, the radial direction cross section of the second pipe 38 (the injection pipe 43) including the injection orifice 37 is set to be greater than the radial direction cross section of an inside of the supply pipe 45 which is a minimum cross section of the first pipe 36.

As described above, also in the fifth embodiment, in the same way as the first embodiment, since the passage cross section of the second pipe 38 is set to be greater than that of the first pipe 36, it is possible to increase the cooling efficiency.

As a modified example of the fifth embodiment, as shown in FIG. 18, a radial direction cross section of a part 46 of the supply pipe 45 is narrowed or squeezed so as to have an orifice shape. Also in this case, a minimum radial direction cross section of the part 46 of the supply pipe 45 can be smaller than the cross section of the injection orifice 37.

FIG. 19 shows a six embodiment in which the present invention is applied to a die-cast type oil jet. In this embodiment, two injection nozzles 32 each having at a tip end thereof the injection orifice 37 are formed integrally with the oil jet body 30 such that the engine oil is supplied to both pistons of right and left banks of a V-type internal combustion engine. The present invention can be applied to such a die-cast type oil jet.

Next, distinctive structure and effect of the above embodiments will be described.

[1] As shown in FIG. 4, the injection nozzle 32 has the first pipe 36 having the supply port 35 communicating with the oil supply passage 26 side and the second pipe 38 having the injection orifice 37 injecting or spraying the engine oil. These first pipe 36 and second pipe 38 are connected or joined together with their axes forming a predetermined angle. Then, the injection nozzle 32 is formed such that the cross section of the injection orifice 37 is greater than the minimum radial direction cross section of the first pipe 36.

Therefore, the injected engine oil is mixed with air, and the flow of the engine oil becomes spray of particulate droplets. As a result, the injection range (the injection area) of the engine oil is broadened, and the engine oil widely contacts or adheres to the back surface side of the piston crown surface 15. A piston temperature reduction effect is therefore greatly increased. By the reduction in piston temperature, degradation of strength of the piston itself at a high temperature can be suppressed, thereby improving reliability. Further, since a temperature of the piston crown surface 15 is decreased, an engine knocking is also suppressed.

[2] Further, the injection nozzle 32 is formed such that the minimum radial direction cross section of the second pipe 38 is greater than the minimum radial direction cross section of the first pipe 36. Therefore, as shown in FIGS. 5A to 5D, when the engine oil flows from the narrow first pipe 36 into the wide second pipe 38 and collides with or strikes a wall surface of the second pipe 38, the turning flow is generated. By this turning flow, the injection range of the engine oil is further broadened.

[3] Moreover, the oil jet 23 for the internal combustion engine is configured such that when the pressure of the engine oil supplied to the oil supply passage 26 of the internal combustion engine is equal to or greater than a predetermined value, the engine oil spontaneously jets.

Since the engine oil spontaneously jets by the oil pressure in this manner, a structure of the oil jet can be simplified without requiring an electromagnetic valve. In a case of such a hydraulically actuated oil jet, the engine oil is injected also at an engine start at which the oil pressure is high. Here, as shown in the reference example of FIG. 6A, in a case of a conventional oil jet that jets the engine oil linearly, the engine oil flows so as to spread toward the back surface side of the piston crown surface from an oil adhesion point. In contrast to this, in a case of the oil jet of the present embodiments as shown in FIG. 6B, since the particulate droplets of the engine oil are injected, the engine oil contacts or adheres to the piston back surface side in layers, and an oil adhesion time lengthens, thereby promoting the heat exchange. Consequently, the oil itself easily absorbs temperature, and oil temperature is easily increased. This helps increase in oil temperature at the engine start, and a viscosity of the oil can be decreased. Hence, fuel efficiency at the engine start can be improved.

[4] As shown in FIG. 4, the second pipe 38 is formed linearly up to the injection orifice 37. Therefore, since the droplet formed by inflow of the engine oil from the first pipe 36 into the second pipe 38 is injected as it is from the injection orifice 37, the particulate droplet of the injected oil can be easily obtained. In addition, the second pipe 38 can be readily formed by drilling.

[5] Likewise, the first pipe 36 is also formed linearly. Therefore, inertia force in the axial direction of the engine oil flowing in the first pipe 36 is strengthen, and this promotes generation of the particulate droplet when the engine oil collides with the inner wall surface of the second pipe 38. In addition, the first pipe 36 can be readily formed, for instance, by drilling.

[6] Preferably, the first pipe 36 and the second pipe 38 are connected or joined together with their axes forming 30 degrees or more. This structure promotes generation of the particulate droplet when the engine oil having flown in the first pipe 36 collides with the inner wall surface of the second pipe 38.

[7] As shown in FIG. 7, when the minimum radial direction cross section of the second pipe 38 is four times the minimum radial direction cross section of the first pipe 36 or more, as shown in FIG. 5D, the cavity 40 is generated in the second pipe 38, and this promotes generation of the droplet of the injected engine oil.

[8] Furthermore, in the second embodiment shown in FIG. 8, the axis 36A of the first pipe 36 is offset from the axis 38A of the second pipe 38. By this offset structure, as shown in FIGS. 9A to 9D, the turning flow Y1 is strengthen, and the injection range (the injection area) of the engine oil is further broadened.

[9] If the offset amount e of the axis 36A of the first pipe 36 from the axis 38A of the second pipe 38 is too large, the turning flow of the injected engine oil is too strong, then linearity of spray becomes weak. As a consequence, there is a risk that the flow of the injected engine oil cannot reach the back surface side of the piston crown surface 15. Therefore, as shown in FIG. 12, it is preferable that the offset amount e be set to 15% or less with respect to the diameter (the outlet bore) of the second pipe 38.

As the oil jet for the internal combustion engine based on the embodiments explained above, for instance, the followings are raised.

As one aspect of the present invention, an oil jet for an internal combustion engine, which is provided inside the internal combustion engine and injects engine oil toward a back surface side of a piston, the oil jet comprises: an injection nozzle that injects the engine oil supplied from an oil supply passage of the internal combustion engine toward the piston, and the injection nozzle has a first pipe communicating with an oil supply passage side and a second pipe having an injection orifice that injects the engine oil, and the first and second pipes are joined together with axes of the first and second pipes forming a predetermined angle, and the injection orifice is formed such that a cross section of the injection orifice is greater than a minimum radial direction cross section of the first pipe.

As a preferable aspect of the present invention, the second pipe is formed such that a minimum radial direction cross section of the second pipe is greater than the minimum radial direction cross section of the first pipe.

As another preferable aspect of the present invention, the oil jet for the internal combustion engine is configured such that when a pressure of the engine oil supplied to the oil supply passage of the internal combustion engine is equal to or greater than a predetermined value, the engine oil is injected.

As a preferable aspect of the present invention, the second pipe is formed linearly.

As a preferable aspect of the present invention, the first pipe is formed linearly.

The first and second pipes are joined together with the axes of the first and second pipes forming, for instance, 30 degrees or more.

As a preferable aspect of the present invention, the second pipe is formed such that the minimum radial direction cross section of the second pipe is four times the minimum radial direction cross section of the first pipe or more.

As another preferable aspect of the present invention, an axis of the first pipe is offset from an axis of the second pipe.

As another preferable aspect of the present invention, an offset amount of the axis of the first pipe from the axis of the second pipe is set to be equal to or less than 15% with respect to a diameter of the second pipe.

As another preferable aspect of the present invention, the second pipe is molded into a long hole shape by a plurality of drilling processes.

As a further preferable aspect of the present invention, the second pipe is formed into a cone shape whose radial direction cross section is gradually increased toward the injection orifice.

From another viewpoint, a piston cooling device for an internal combustion engine, which is provided inside the internal combustion engine and injects engine oil toward a back surface side of a piston, the piston cooling device comprises: a supply pipe supplied with the engine oil from the internal combustion engine; and an injection pipe communicating with the supply pipe and having an injection orifice injecting the engine oil toward the piston, and the injection orifice is formed such that a cross section of the injection orifice is greater than a minimum radial direction cross section of the supply pipe.

As a preferable aspect of the present invention, the supply pipe has a part whose radial direction cross section is squeezed so as to have an orifice shape.

As another preferable aspect of the present invention, the supply pipe is formed such that a radial direction cross section of a connecting portion with the injection pipe is small.

From another viewpoint, an oil jet for an internal combustion engine, which is provided inside the internal combustion engine and injects oil toward a back surface side of a piston, the oil jet comprises: an injection nozzle that injects the oil supplied from an oil supply passage of the internal combustion engine toward the piston, and the injection nozzle has a first pipe communicating with the oil supply passage and a second pipe having an injection orifice that injects the oil, and the first and second pipes are joined together with axes of the first and second pipes forming a predetermined angle, and

an axis of the second pipe is offset from an axis of the first pipe. 

1. An oil jet for an internal combustion engine, which is provided inside the internal combustion engine and injects engine oil toward a back surface side of a piston, the oil jet comprising: an injection nozzle that injects the engine oil supplied from an oil supply passage of the internal combustion engine toward the piston, and the injection nozzle having a first pipe communicating with an oil supply passage side and a second pipe having an injection orifice that injects the engine oil, and the first and second pipes being joined together with axes of the first and second pipes forming a predetermined angle, and the injection orifice being formed such that across section of the injection orifice is greater than a minimum radial direction cross section of the first pipe.
 2. The oil jet for the internal combustion engine as claimed in claim 1, wherein: the second pipe is formed such that a minimum radial direction cross section of the second pipe is greater than the minimum radial direction cross section of the first pipe.
 3. The oil jet for the internal combustion engine as claimed in claim 2, wherein: the oil jet for the internal combustion engine is configured such that when a pressure of the engine oil supplied to the oil supply passage of the internal combustion engine is equal to or greater than a predetermined value, the engine oil is injected.
 4. The oil jet for the internal combustion engine as claimed in claim 2, wherein: the second pipe is formed linearly.
 5. The oil jet for the internal combustion engine as claimed in claim 4, wherein: the first pipe is formed linearly.
 6. The oil jet for the internal combustion engine as claimed in claim 5, wherein: the first and second pipes are joined together with the axes of the first and second pipes forming 30 degrees or more.
 7. The oil jet for the internal combustion engine as claimed in claim 2, wherein: the second pipe is formed such that the minimum radial direction cross section of the second pipe is four times the minimum radial direction cross section of the first pipe or more.
 8. The oil jet for the internal combustion engine as claimed in claim 5, wherein: an axis of the first pipe is offset from an axis of the second pipe.
 9. The oil jet for the internal combustion engine as claimed in claim 8, wherein: an offset amount of the axis of the first pipe from the axis of the second pipe is set to be equal to or less than 15% with respect to a diameter of the second pipe.
 10. The oil jet for the internal combustion engine as claimed in claim 2, wherein: the second pipe is molded into a long hole shape by a plurality of drilling processes.
 11. The oil jet for the internal combustion engine as claimed in claim 2, wherein: the second pipe is formed into a cone shape whose radial direction cross section is gradually increased toward the injection orifice.
 12. A piston cooling device for an internal combustion engine, which is provided inside the internal combustion engine and injects engine oil toward a back surface side of a piston, the piston cooling device comprising: a supply pipe supplied with the engine oil from the internal combustion engine; and an injection pipe communicating with the supply pipe and having an injection orifice injecting the engine oil toward the piston, and the injection orifice being formed such that across section of the injection orifice is greater than a minimum radial direction cross section of the supply pipe.
 13. The piston cooling device for the internal combustion engine as claimed in claim 12, wherein: the supply pipe has a part whose radial direction cross section is squeezed so as to have an orifice shape.
 14. The piston cooling device for the internal combustion engine as claimed in claim 13, wherein: the supply pipe is formed such that a radial direction cross section of a connecting portion with the injection pipe is small.
 15. An oil jet for an internal combustion engine, which is provided inside the internal combustion engine and injects oil toward a back surface side of a piston, the oil jet comprising: an injection nozzle that injects the oil supplied from an oil supply passage of the internal combustion engine toward the piston, and the injection nozzle having a first pipe communicating with the oil supply passage and a second pipe having an injection orifice that injects the oil, and the first and second pipes being joined together with axes of the first and second pipes forming a predetermined angle, and an axis of the second pipe being offset from an axis of the first pipe. 